Our results so far suggest that seeds of species like oak, hazel, and beech are going to be much more vulnerable than those of shrubs or trees like ash and cherry. We are currently testing this prediction on an operational scale in a direct seeding experiment on a conifer clearfell site in Hampshire.
We are also investigating ways to reduce seed loss due to predation, for example by using approved seed repellents.
Soil type and sowing depth
We are also looking at ways to reduce the detectability of vulnerable species by investigating the relationships between soil type, and safe sowing depth for reduced predation but successful seedling emergence. The importance of soil porosity for the detection of buried seeds is demonstrated in the figure below:
A demonstration of the effects of burial on seed removal of acorns by rodents on a clearfell site.
In the left picture, seven acorns were sown into the organic debris on a conifer clear fell site. Every acorn was removed overnight.
On the right, another set of acorns was sown into the same layer, but the holes backfilled with wet clay; these acorns remained undisturbed despite the mice probably walking across them to get the ones in the right hand picture!